In German Patent No. 169,482, there is a disclosure of a dough-rounding machine in which kneading surfaces are formed by the facing runs of a pair of oppositely movable endless belts. Because the kneading surfaces diverge upwardly, they are able to process pieces of dough of different sizes. By running the belts in opposite directions, the pieces of dough are rotated about an axis which, owing to a small difference in the velocity of the belts, is gradually moved in a direction of advance to the delivery end of the belts. By appropriately selecting the difference in velocity of the belts, the number of revolutions of the pieces of dough during their period of residence between the belts may be adjusted so that the pieces can be subjected to a large number of kneading operations in a machine of short length and so that a plurality of pieces can be simultaneously treated in narrowly-spaced relationship. The kneading surfaces primarily deform the bottom part of the pieces of dough, whereby a taut skin is formed at the top, which causes the rounded dough pieces to maintain a spherical form during the subsequent rising process.